(NaturalNews) The new, full-body security scanners being introduced at airports pose a greater skin cancer risk than governments have previously acknowledged and are especially dangerous to children and pregnant women, a new study has found.

The devices, known officially as backscatter X-ray machines, were introduced after the "Christmas Day Bomber" successfully got an explosive device through conventional airport screening. They use up to eight seconds of X-rays over the entire body to create a three-dimensional, full-body image of anything that passengers might be carrying beneath their clothing. More than a hundred of the scanners have already been rolled out at 32 U.S. airports, and they are being introduced in other countries, as well. The U.S. Transportation Security Administration (TSA) plans to have 450 of the scanners deployed by the end of 2010.

A new analysis of the radiation dose delivered by the machines, conducted by David Brenner and colleagues at Columbia University, found that because the beams concentrate X-rays on the body's skin, the effective dose may be 20 times higher than previously estimated.

Because the skin is one of the body's most radiation-sensitive organs, the scanners significantly increase the risk that passengers will develop basal cell carcinoma, a kind of skin cancer. Children and the 5 percent of adult passengers with certain relatively common gene mutations are at significantly higher risk due to their reduced ability to repair DNA damage.

"If there are increases in cancers as a result of irradiation of children, they would most likely appear some decades in the future," Brenner said.

Basal cell carcinoma normally occurs in the heads and necks of people between the ages of 50 and 70. For this reason, Brenner suggested that, at minimum, these areas of the body should not be scanned.

"The individual risks associated with X-ray backscatter scanners are probably extremely small," he said, "[but if] all 800 million people who use airports every year were screened with X-rays then the very small individual risk multiplied by the large number of screened people might imply a potential public health or societal risk. The population risk has the potential to be significant."

Brenner was a member of the U.S. government committee that originally set the safety guidelines for the devices, and was one of the members who endorsed their use. Brenner now says he never would have endorsed the scanners if he knew there were plans to use them on all passengers.

"There really is no other technology around where we're planning to X-ray such an enormous number of individuals," he warned. "It's really unprecedented in the radiation world."

The British Civil Aviation Authority (CAA) responded to the study by reiterating its position that the scans are safe.

"The device has been approved for use within the United Kingdom by the Department for Transport and has been subjected to risk assessments from the Health Protection Agency," the CAA said. "To put the issue in perspective, the radiation received from the scanning process is the equivalent to two minutes radiation received on a Transatlantic flight. Under current regulations, up to 5,000 scans per person per year can be conducted safely."

The new study is not the first to raise concerns over the devices, however. In February, the Interagency Committee on Radiation Safety issued an internal report to groups including the European Commission, International Atomic Energy Agency, Nuclear Energy Agency and the World Health Organization warning that pregnant women and children should never be exposed to the devices.

"The issue raised by the report is that even though doses from the systems are very low, they feel there is still a need for countries to justify exposures," said Michael Clark of the United Kingdom's Health Protection Agency.

The ability of the devices to produce naked images of passengers has also produced challenges on privacy grounds.